The use of a safety harness does not affect body sway during quiet standing

BACKGROUND: Postural sway during quiet standing reduces when somatosensorial information is provided by an active or passive "light touch" of different body parts with a surface. The contact of the safety harness with the body could induce a similar effect, leading to an undesirable side effect in the balance evaluation. METHODS: This study investigated if a safety harness system, commonly used in balance studies, affects body sway during the balance evaluation. Healthy adults stood as quietly as possible for 60s in a comfortable position on a force plate. First, we performed an experiment on the light-touch effect with 10 subjects to determine the necessary sample size for the main investigation. Then, 60 subjects completed four tasks where the use of the safety harness and the visual information were manipulated. Area, root-mean square, speed, and frequency of the center of pressure displacement were analyzed. FINDINGS: A light touch decreased postural sway on both visual conditions but there was no effect of the use of a safety harness on sway when quietly standing, independent of the visual information. Postural sway increased on both somatosensorial conditions when the visual information was not provided. INTERPRETATION: This result shows that the safety harness does not interfere with the evaluation what is of major importance to methodological aspects of balance evaluation.